What's important to understand here (and what most people don't realize) is that BPL technology, in case you were unaware, has never-the-less been approved for deployment in the U.S. by the Federal Communications Commission and the NTIA, to the dismay of many shortwave radio listeners, amateur radio operators, public safety communication system managers, high seas marine radio users, and military LMR and airborne radio system operators. (Take some time to review these comments from the FCC proceedings on this matter for further background and insight)

This Report presents the results of the work carried out by IST-050/RTG-022, the Research Task Group(RTG) on “HF Interference, Procedures and Tools”, to address the concerns raised by the potential forunintentional radio interference to be caused by the widespread operation of broadband wire-linetelecommunications systems.

PowerLine TeleCommunications (PLT, PLC) and various forms of Digital Subscriber Line (xDSL)transmissions use the existing mains electricity or telephone wiring including in-premises cables fortelecommunications with data rates higher than 1 MBit/s. As these lines were not designed for suchbroadband transmissions, they will cause unintentional RF emissions which may adversely affect theestablished radio noise floor directly, or by cumulative propagation from many such sources. The existingHF background noise possibly may be increased via ground wave and/or sky wave propagation.

Increase of the existing HF noise floor by widespread use of PLT and/or xDSL will bring up problems forMilitary Radio Users as well as for HF Communication Intelligence (COMINT) in all NATO countries.The signal-to-noise ratio thus may be reduced for tactical and strategic HF radio as well as for fixedsensitive COMINT sites.

Exact calculations of HF radio noise emissions from the new broadband wire-line telecommunicationsnetworks were impossible because of missing models for these transmission systems. Therefore methodshave been investigated to find procedures, models and tools applicable for being able to determine theinfluence of PLT and xDSL on reception of HF radio signals. These are described in this report.

The RTG addressed itself to the HF radio emission effects of the new broadband cable transmissions.It investigated and found means that allow calculation of cumulative field strengths of HF noise radiatedby PLT or xDSL. This will enable NATO and its nations to determine the threat to military HF radiocommunications and COMINT systems from PLT and xDSL and to take the appropriate steps. It shouldbe noted here that the determination of the nature and the severity of any possible detrimental effect uponthe military systems was outside the RTG’s expertise and ToR.

The RTG chose to concentrate its work on the PLT issue rather than xDSL because PLT will produce themost problems regarding HF interference (power lines have less symmetry and will have impedancediscontinuities), they will be deployed in large numbers, and finally the current versions of xDSL have nodocumented HF interference-causing problems, while the VDSL variants covering the entire HF range arestill in the definition phase.

In the course of the studies, the RTG determined that ITU-R P.372-8 noise curves (based onmeasurements carried out in the 1970s) are still valid in Europe. Recent measurements carried out inGermany and Great Britain indicated that there is no remarkable difference between these measurements,specifically no increase of the ambient noise in quiet rural zones within the last 30 years.

Based on these measurement results, the cumulative interference field strengths far away fromtelecommunication networks should not be higher than–15 dBìV/m(9 kHz bandwidth) across the entireHF range, if no measurable increase in minimum noise levels are to be tolerated. The RTG refers to thiscriterion as theAbsolute Protection Requirement. It should be noted that this value is in the range of 10 to1 dB below the ITU-R P.372-8 Quiet Rural noise curve, which are median values, across the HF band.

A couple of important tasks in the RTG’s work, namely, the appropriate measurement techniques and themost suitable propagation path loss models for interference studies, were addressed and completed.

The quantity of interest when considering cumulative effects in the far-field is the EIRP (equivalent(or effective) isotropic radiated power) per unit bandwidth caused by each signal source, in units ofdBm/Hz, at different frequencies. The radiation pattern might also be of interest in some cases, but whensumming up many different sources with different wiring geometries over a wide area, it is reasonable toapproximate the average radiation pattern as isotropic (in elevation as well as in azimuth).

In modeling the emissions from an overhead Access PLT line, the PLT wires can be modeled as asuccessive set of dipoles, assuming that the standing waves present are the dominant emission source.Given the PLT geometry, the cylindrical coordinate system is more practical rather than the sphericalcoordinate system generally used in electromagnetics. In the vicinity of a PLT, up to 200 metres, the useof the expression for the exact solution of a dipole is recommended, which is valid at any distance in bothnear-field and far-field.

The RTG has developed a “Cumulative PLT Tool”, which was used to perform cumulative PLT noisecalculations at several hypothetical sensitive receiver locations. For each receiver location and frequency,the percentage of parameter combinations was computed where the estimated cumulative PLT noise levelis above the quiet rural level, above quiet rural +6 dB, and above the rural noise level. The resultsindicated the following:

a) High probability that PLT would cause increased noise levels at sensitive receiver sites given theprojected market penetration; and

The percentage of parameter combinations was also computed where the estimated PLT noise level isabove the Absolute Protection Requirement. Again, the probability of the cumulative effect of PLTexceeding the Absolute Protection Requirement is predicted to be relatively large for all frequencies andreceiver locations investigated.

Currently, there are no commonly accepted regulatory emission limits for PLT. While it is highlydesirable that the regulatory limits on PLT emissions be harmonized throughout the NATO countries,the RTG recognizes that NATO, by itself, has no regulatory authority over the emission limits. Therefore,it is recommended that NATO seek the implementation of this goal by working together with the nationaland international regulatory authorities."

The complete NATO report sheds additional detailed information on this matter and should be of interest to those concerned with "spectrum pollution" matters.

Saturday, September 15, 2007

Radio (RF) spectrum is key to the future success of (wireless) radiocommunications. It is a valuable commodity and a unique, shared resource. Unlike other natural resources, it can be repeatedly reused - if certain technical conditions are met and user regulations are followed.

In practice though, it is a finite resource, accommodates a limited number of simultaneous users, and requires careful planning and management to maximize its value for all services and users — especially since worldwide demand for communication spectrum is increasing rapidly.

Many new wireless technologiespresent significant challenges to the development of prudent business models as well as to long-established regulatory schemes for spectrum allocation and management.

Rigid spectrum allocation policies limit innovation and cannot readily accommodate pressing needs for more commercial bandwidth. Operators look to evolve technologies that support their business cases. Licensing or policy making that would not allow this natural evolution or mandate a particular technology in a particular band is too rigid for many operators. New generation infrastructure and terminals must support ever wider ranges of frequencies, harmonized or not, to meet highly heterogeneous frequency plans in markets around the world. Terminals will need to operate worldwide and comply with numerous regulatory environments and market opportunities, thus supporting frequency allocation and heterogeneous technologies. New technologies such as software-defined radio (SDR) or cognitive radio (CR), wideband power amplifiers and filters are already available in the infrastructure and will soon be available in terminals, supporting frequency heterogeneity with minimal additional cost.

Within this context, traditional ways to assess the merits of new technical solutions, and allocate and tax frequency use are inadequate. Consequently, this presents major challenges in the introduction of new technologies and efficient spectrum use, such as ensuring new spectrum is only assigned when really needed.

This 2006 Alcatel-Lucent white paper describes a new concept known as DSM (Dynamic Spectrum Management) which would enable wireless operators to dynamically access appropriate spectrum to deliver new wireless services, while providing greater choices for spectrum users. It provides an overview of DSM from the engineering, technology, economic and radio policy aspects and considers critical parameters that impact its implementation.

The paper should be required reading for anyone involved with or concerned about current methods of spectrum regulation and allocation in the U.S., and, perhaps even more importantly, with how any spectrum management methods chosen will ultimately serve to protect this resource from eventual political and economic oversell.

Monday, September 10, 2007

Those concerned or interested in learning more about spectrum regulation and frequency allocation policies and their impact on radio and wireless communication devices and users in the U.S. may want to begin paying very close attention to the Notices, actions and decisions made by the FCC's Wireless Telecommunications Bureau (WTB), their new Public Safety and Homeland Security Bureau (PSHS), and, their Office of Engineering and Technology (OET). More background information on spectrum policy, including the latest on the 700 MHz proceeding, can be found on the FCC's Spectrum Policy Task Force site. And, there's always the FCC's Daily Digestwhich provides a brief synopsis of Commission orders, news releases, speeches, public notices and all other FCC documents (with links to the full text of each) that are released each business day.

Finally, this 2006 paper Regulating Spectrum Management: Overview and Trendsis intended to provide readers with a broad overview of wireless communications spectrum management concepts and issues, including a review of differences between traditional spectrum management methods and policy and recent innovations and practices due to technology advances. The approach taken is more descriptive than prescriptive, allowing readers to make up their own mind on various perspectives. It's interesting to note that the authors have found that there are no standard solutions that fit every situation.

An introduction to spectrum management including best practices and considerations involved in the use and regulation of radio frequency spectrum. An outline of policy and planning considerations including technical standards and the allocation of spectrum.

The authors offer some interesting perspectives on the age-old problems associated with LMR system interoperability (a "hot topic" today, particularly when considering the current state of Public Safety radio system interoperability in much of the U.S.), a historical account of FCC and NTIA spectrum regulation and policy, the lack of innovation in frequency allocations, and more.

They also make the suggestion that an emerging new technology known as Cognitive Radio(a term first coined in 1991 by Joseph Mitola) could improve spectrum efficiency and spectrum availability for all users in the VHF and UHF LMR bands. Here is the abstract:

"The frequency bands that have been licensed to the land mobile radio (LMR) services for decades are a tremendously fertile field for the deployment of cognitive radio technology. This paper outlines several reasons why policy-based cognitive radios would be particularly useful for modern public safety, federal non-military and business/industrial applications, especially in the VHF and UHF bands, where 80% of the public safety, federal and business/industrial licenses are currently held.

This paper argues that many interoperability deficiencies are directly related to the original approach to spectrum policy and radio frequency regulation developed in the early 1920's, which segmented uses of LMR spectrum into several use classes. It provides a historic perspective to explain why the current status of LMR infrastructure, operations and licensee behavior is a direct result of antiquated policies and technologies still applied and deployed in these bands. The paper discusses the reasons that cognitive radio could be a successful solution for the apparent congestion in the bands. It suggests that policy-based cognitive radio systems operated on a cooperative, shared basis could lower costs of use and aid coordination for emergency responders across both public and private sectors of the traditional LMR user community.

We discuss policy reforms and innovations such as spectrum pooling and spectrum portability that could spur new shared infrastructure development and spectrum efficiencies. We suggest several key policy reforms for consideration, including immediate cessation of ongoing narrowbanding initiatives, decoupling of spectrum licenses from spectrum access, and national spectrum management by frequency coordinators."

The paper (12 pages) is well worth the time to review for those interested or concerned with spectrum matters.

Wednesday, September 5, 2007

There were a few provocative(?) insightful (?) revealing (?) stories in the media today regarding the FCC's public communications skills....

This AP story by John Dunbar "FCC's Methods Leaves Public in the Dark" suggests "It's odd for an agency that has the word "communications" as its middle name" to "routinely leave the public in the dark about how it makes critical policy decisions".

Cynthia Brumfield at The IP and Democracy site follows up with a claim that "the FCC is the worst communicator in Washington". "Clear answers are rare and, indeed, FCC rules dictate that agenda items (those issues to be voted upon by the Commissioners) are “non-public” information. Employees can get fired if they disclose anything the FCC is planning". She also provides links to a couple of additional pieces written by Ted Hearn at MultiChannel News who labeled the agency the “Federal Incommunicado Commission”.

She adds even more fuel to the fire by ranking the Commissions web site as a "nightmare"--- a real nightmare.

Frankly, I don't understand what all the hullabaloo is about. The FCC long ago abdicated its responsibility to openly communicate with the general public (along with certain other spectrum management related duties) and is now the best corporate and special interest facilitating entity that money and lobbying can buy. I guess some folks just can't get used to the way business is done at the Portals these days, but I can assure you that there's good reason for it. Just continue on as usual (spectrum matters are out of your league, anyway, right?) and everything will turn out just fine....

"Spectrum management is an exercise in balancing disparate stakeholderinterests through effective user education and the enforcement of regulatory policies that reflect practical reality, political responsibility, economic common sense, and a basic understanding of the laws of physics."

About this Blog

news, insight, and opinion from a variety of both well-known and not-so-widely-known or reported industry sources, offered to provide added perspective, context, and a clearer understanding of why the wireless (RF) spectrum, technology trends, and regulatory policy should not be taken for granted - spectrum matters

About the Blogger

General Manager - Systems Group -
Quality MobileCommunications, LLC
A professional 30+ year career in the Private Wireless, Commercial LMR/SMR Two-Way Radio, and Mobile Communications segments of the wireless communications industry provides the basis for many of the thoughts and comments that may occasionally be posted here.